Apparatus for operating metallurgical furnaces



April 18, 1961 J. H. sTRAssBuRGER 2,980,416

APPARATUS FOR OPERATING METALLURGICAL FURNACES 3 Sheets--Sheei'l l Filed June 5, 1958 m UmDOm ZmO XO am .rm-2 OlE m UEDOm JUL/Us H STRASSBURGER A TTORNEV April 18, 1961 J. H. sTRAssBURGER 2,980,416

APPARATUS FOR OPERATING METALLURGICAL FURNACES Filed June 5, 1958 3 Sheets-Sheet 2 LOW STEAM CONTROL FLOW MOISTURE INVENTOR.

Q JUL/Us H sTRAssBz/RGER April 18, 1951 J. H. sTRAssBURGER 2,980,416

APPARATUS FOR OPERATING METALLURGICAL FURNACES Filed June 5, 1958 3 Sheets-Sheet 5 SOURC E BLOWER HIGH PRESS STEAM SOURCE INVENTOR.

N JUL/US H STRASSBURGEP H By Shaw-5W ATTORNEY United States Patent Julius H. Strassburger, Steubenville, Ohio, assignor to National Steel Corporation, a lcorporation of Delaware Filed June 5, 1958, Ser. No. 740,052

15 Claims. (Cl. v266--30) This invention relates to blast furnaces and more particularly to apparatus for controlling the composition of blast gas for such furnaces.

It is known that improved performance may be obtained from blast furnace installations by enriching blast gas with oxygen or by introducing blast gas at elevated temperatures into the furnace, providing sufficient moisture is added to the blast gas to insure smooth furnace operation. The quantity of moisture required in blast gas in order to maintain a smooth operating furnace blown with oxygen enriched blast gas or blast gas at an elevated temperature depends upon the percent of oxygen enrichment and the temperature of the blast gas, the quantity of necessary moisture being greater as the oXygen enrichment or the blast temperature increase. In the copending application of Julius H. Strassburger, Serial No. 736,468 led May 20, 1958, for Method of Operating Metallurgical Furnaces there is disclosed the quantity of moisture required for different percentages of oxygen enrichment and for dilferent blast gas temperatures. In particular, with a blast gas temperature of about 1100 F. the required moisture may vary from about 3 grains to about 40 grains per cubic foot of blast gas as the oxygen enrichment Varies from 1% to 10%, while with blast gas at a temperature of 1200 F. to 2500 F. and containing from 1% to 10% oxygen enrichment the required moisture may be as low as about 7.3 grains per cubic foot of blast gas and as high as about 82.2 grains per cubic foot of blast gas.

Blast furnace installations ordinarily include a number of steam driven prime movers and accordingly a large quantity of exhaust steam at substantially atmospheric pressure is available as an inexpensive source of aqueous fluid for providing the required blast gas moisture. The low pressure exhaust steam may be mixed with atmospheric air fed to the suction side of a compressor for blowing blast gas through the tuyeres and into the furnace. Since the quantity of moisture that may be added to blast gas on the suction side of the compressor is limited, for the most part, by the existing temperature, it is not possible to meet the moisture requirements by the use of low pressure steam except when the blast gas is blown to the furnace at relatively low temperature and contains low percentages of oxygen enrichment. High moisture requirements have been satisfied in the past by introducing high pressure steam to blast gas on the discharge side of the compressor. Steam under a su'iciently high pressure for this purpose is not available in blast furnace installations as waste steam and the power required to provide an adequate source of high pressure steam constitutes a material expense item in View of the large volume of moisture blown into the furnace during each twenty-four hour operating period.

The present invention provides a novel apparatus by which the required moisture content of blast gas is obtained in such a manner as to utilize at all times the maximum possible quantity of low pressure steam irrespective of the temperature and natural moisture content 2 of atmospheric air. This is accomplished by the provision of means for adding low pressure steam to blast gas on the suction side of the compressor and for adding high pressure steam to blast gas on the discharge side of t-he compressor, and the provision of a novel control apparaus which functions to maintain a predetermined quantity of moisture in blast gas blown to the furnace irrespective of variations in natural moisture content of the atmospheric air while at the same time insuring that the maximum possible quantity of the moisture in the blast gas is supplied from lthe source of inexpensive, low pressure steam.

The foregoing and other objects and features of the present invention will appear more fully from the following detailed `description considered in connection with the accompanying drawings which disclose several embodiments of the invention. It is to be expressly understood, however, that the drawings are designed for purposes of illustration only and not as a definition of the limits of the invention, reference for the latter purpose being had to the appended claims.

ln the drawings, in which similar reference characters denote similar elements throughout the several views:

Figure l is a diagrammatic view illustrating a blast furnace installation embodying the principles of the present invention;

Figure 2 is a diagrammatic view illustrating a blast furnace installation constructed in accordance with another embodiment of the present invention, and

Figure 3 is a diagrammatic showing of a blast furnace installation including a further embodiment of the present invention.

With reference more particularly to Figure l of the drawings, a blast furnace installation constructed in accordance with the principles of the present invention iS disclosed therein including a blast furnace 10 having a vertical substantially cylindrical stack 11 provided with a large bell 12 and a small bell 13 for facilitating the charging of solid burden into the top of the furnace. At the top of the stack 11 one or more takeolf pipes 14 are provided for conducting -top gas from the top of the furnace. The stack is supported at its lower end by a plurality of pillars 16 arranged around the lower periphery of the furnace. At the lower end of the furnace there is a hearth 17 supported by base 18, and between the hearth and the stack a bosh 20 is provided. A bustle pipe 22 encircles the lower portion of the furnace for supplying blast gas under pressure to the hearth. A plurality of tuyeres 23 are positioned around the upper portion of the hearth and project through the walls delining t'he hearth. The tuyeres 23 are connected by blow pipes 24 to the bustle pipe 22 so that compressed blast gas fed to the bustle pipe flows through the blow pipes and then through the tuyeres and into the furnace hearth. Molten slag and iron collects in the hearth and a tap hole 27 is provided for periodically tapping molten slag from the furnace. An iron notch 28 is provided in the hearth at a level below .the tap hole 27 through which molten pig iron is periodically removed from the furnace.

Compressor means, such as a blower 30 is provided for compressing blast gas for the furnace. The blower 30 may be driven by a steam engine or an electric motor 32 connected to the blower through a shaft 33. Blast gas discharged from the blower 30 is conducted by conduit 34 to suitable stove means, not shown, for preheating the blast gas. The stove means may be of conventional construction including a plurality of individual stoves that are heated by burning top gas from the furnace and then used to preheat the blast gas, and a by-pass pipe may be provided for controlling the blast gas temperature. Heated blast gas from the stove means is conducted through conduit 35 to the bustle pipe 22 VVfor distribution to the tuyeres. YThe suctionpside 36 of the blower-30 1s connected to one end 37 of a'conduit 3S which communicates atfits-other end-39,with af'sourceofblastgas.suchV asfatmospheric air. A lter 40Y mounted inra/casing41.

mayvbe providedinthe conduit'38. adjacentits end 39lto l remove dirt. and-.dust .from the 'enteringain Y and 45. The-venturi;measuring'device maybe'of conventionalconstructionand may. include acompensator- 46 connected to the loading lines 44 and '45. by ,conduits` 47'. v The compensatorfr functions to .indicateV in. what manner-ther-venturi-l indications must be changed to com-` pensatefordeviationsinbarometric pressure and temi Y perature relativetofthe designed constants. The blower control 43Ymay also be of conventionalv construction and mayjpreferably be of the type including a calibratedr manually 'operable element for determining the desired blower. output intermsof cubic feet of blast gas per minute, for'example. Setting ofthe manually operable element establishesia proportional force which is applied against alforce derived from the venturi measuring device 42 which` is proportional to therate of flow: of blast Ygas through'vthe conduit 38; Unbalancing `of these forces produces a control signal of the proper characteristic which is transmittedto thermotor 32 through lead '48 to increasefor decrease'the output of the blower and maintain the rate of flow through the conduit 38` equal to the desiredrate` of flow as determined by the calibrated manually operable elementof the blower control'43. In this typeof control the loading lines 49 and 50 are usually connected to closed 'chambers having a common diaphragm wall which-moves in opposition to the force establishedfby thel manually Voperable element; With suchxarrangement a predetermined quantity of blast gas may -be' constantlyY maintained automaticallywith only slight adjustmentsnecessary yto compensate the variationsintemperature and barometricfpressure. Also, the operator may easily determine thequantity ofblast gas fromV a gauge-indicating directly the rate of flow of blast gas-fasV determined by the. venturi device 42 and the operator may readily change the-rate of flow as required by merelyl adjusting calibrated manually'operable element of the'blowerrcontrol- 43; Y Y

purity, for example. The oxygen stream from the source 52 is passed through a ow meter 53, a conduit 54 and l oxygenY enrichment in the composite stream blown tothe furnace vthrough the conduit E35v will dependffor the most part uponrthe position Vof the oxygen `control valve 55. A system is provided Vfor regulating `the valve 55 to establish and maintain substantially constant-predetermined ,percentages of oxygen enrichment of the composite stream. For this purpose a ratio control 56 is porvided which operates --responsively to the rate of ilow of liuid through the compressor 30 and to the Yrate of flow of the oxygen stream as determined by the venturi measuring device42, and the flow meter 53,l respectively, to

Blast gas blown through the'conduit 35 into the fur- Y nace-comprises ,av composite stream formed by `combining with theV stream of atmospheric air owing through'the conduit 38 streams of'oxygen'or oxygen enriched gas and aqueous iluid-such as steam. The oxygen enriching stream is' controlled relativeto blast gas owing through the 'compressor so that the composite stream blown to Vthefurnace comprises a predetermined portion of oxygen which may be varied'through iixed limits. 4Also, aqueous fluidis introduced in such a manner as to establish a constant-moisture content' inthe composite stream, which may be varied, irrespectiveof'the degree of natural moisture in the atmospheric air. VThe composite stream may beformedso that a constant mass'ofi blast gas may be continually blown into the furnace irrespective of variationsV in the natural moisture content of the atmospheric air orV of changes in the'required quantity of moisture and the desired percentage of oxygen enrichment of the blast gas. Y Y

added to the atmospheric air owing through the conduit 38 byfmeans of a conduit 50 which may have its discharge end 51v terminated within the conduit 38.0n the upstreamv side ofthe venturimeasuring device 42. 'The oxygen, may be derivedV from any suitable sourcel 52 .which-Amay' comprisean" air kfractionating apparatus cap- .ahlecfcproducng aflargenuantity of `oxygen/of 90% produce a. proportional control signal which determines positioning of the oxygen control'valve 55'throughk operation of a suitable transmitterf57. The ratio control 56 may be of anyY suitable 'conventional constructionfand maybesimilar to the blower control v43 described above in whichcase a diiierentialpr'essure actuateddiaphragm controlled by the oxygenrowrneter would replace the manually operableelement 'and'4 the, desired proportioning would .'beobtained by adjusting-spring biasing means in a conventionalgmanner. Specifically, loading line 58 connected tothe venturimeasuring ydevice-l2r and loading line 59,lconnected to the ilow meter153 communicatetwith individualk chambers spaced byY common diaphragms moving in opposition and` being adjustably biased to maintain a desiredpercentage relationship betweenthe oxygenowandthe rate of flow of blast gas. Resultant movementY ofi the diaphragmsvmay ybe transmitted by means ofv a mechanical, hydraulic or electric medium 60 to thetransmitterf57-Y-for controlling the valve 55.V With this arrangement the oxygen streamentering the conduit 38 may beaccurately controlled solthat` the composite stream includesa iiXerd kpercentage of oxygen as determined by the desiredse'ttingA ofthe ratio control 56.

' Innaccordance with the principles ofthe present invention, moisture necessary-Sto establish a desired moisture contentrofblast gas blown to the furnaceis obtained Y from, a source of lowpressure steam, or from a source Vthrough YanovelV arrangement by which the maximum quantity of available. low pressure steam is at all times utilized to, meetfthe moisturelrequirements and the flow of'lowV pressure steam or the ow of high pressure steam is controlledto -maintain;the total moisture content of blast gas blownfto the furnace substantially equal to a predetermined value irrespective of, variation of the naturalV moisturev content of the Y atmospheric air. As shown, steam from a low pressure source is conducted by conduit -66.to a flow meter 67, thepurpose of which willbefdescribedl below. From the ilow meter 67, the steam is conductedby conduit 66 to a low pressure steam control valve 69and thence through conduit 70 whichv hasoa. dischargeend v71 terminated within the conduit 38 at aposition whichy may be upstream of the Y .l A stream of oxygen orV oxygen enrichedgas may be Y venturi measuring device42, as shown, thelconduit 70 including a control. valve 72. AV dew cell 73 isrin fluid communication throughconduit 74iwithin the conduit 3S downstream of the discharge end 71 of the conduit 70 for the'purposeof measuring the moisture content ofV blast.. gas at that point in the system. The output of the dew cell is conducted by lead 75 to a transmitting device 76 coupled to position the valve 69. With this arrangement the control valve '69 is automatically adjusted to at all times permitthe maximum ow of steam to theV conduit 70without condensation ofY water inV the conduit38. A. The. valve 72 is controlled by a transmitting device 71connectedthrough lead178, switch. 794 and .lead

80 to a moisture control device 81. The moisture control device is fed with a control signal from a dew cell 82 through a lead 83 and the dew cell is connected to within the conduit 34 downstream of the discharge of the compressor 30 through a conduit 84. The dew cell `82 (and also the dew cell 73) may be of conventional construction and may comprise a humidity sensitive cell that may be adjusted to produce an output signal proportional to the absolute humidity of blast gas flowing through the conduit 34, the output signal being fed through lead 83 to the moisture control device 81. The moisture control device may also be of conventional construction and may be similar to the blower control 43 described above. With this type of control the signal supplied by the dew cell, which is proportional to the moisture content of the blast gas, is converted into a force which is balanced against a force proportional to a predetermined or desired moisture content value established by the position of a calibrated manually operable element. An error signal is generated responsively to any difference between the forces and the error signal is transmitted by lead 80, switch 79 and lead 78 to the transmitter 77 for adjusting the position of the valve 72. With this arrangement the moisture control 81 is adjusted by proper setting of its manually operable element to maintain a desired moisture content, such as grains per cubic foot of blast gas, for example. Thereupon, assuming the natural moisture in the air entering conduit 38 produces 4 grains of moisture per cubic foot of blast gas, the valve 72 would be automatically adjusted to provide a ow of steam suiiicient to add a moisture content of 6 grains per cubic foot to the blast gas. Should the natural moisture content of the air change under these circumstances, the valve 72 would be automatically moved to the required position to maintain a supply of aqueous fluid to the blast gas equal to the difference between the desired moisture content and the natural moisture in the atmospheric air.

A source of high pressure steam 90v is provided together with an arrangement for adding high pressure steam to the blast gas when the desired moisture content is greater than that that may be maintained from the source of low pressure steam. Stream from the high pressure source is conducted through conduit 91, ilow meter 92, conduit 93, control valve 94 and into conduit 95 which has a discharge end 96 terminated within the conduit 34 on the discharge side of the compressor 30. The valve 94 is controlled by a transmitting device 97 Which operates in accordance with a signal lfrom the moisture control 81 conducted thereto through lead 80, switch 79 and lead 98. The switch 79 may occupy a first position in which the lead 80 is connected only to the lead 78 or a second position in which the lead 80 is connected only to the lead 98, and the switch 79 is moved to the rst position or the second position by a transmitting device 99. The transmitting device 99 is connected to switches 100 and 101 through leads 102 and l103, respectively, and the switch 100 is operatively connected to the transmitting device 77 of the low pressure steam supply while the switch 101 is operatively connected to the transmitting device 97 of the high pressure lsteam supply. When the valve 72 is in closed position the switch 100 is positioned to effect energization of the transmitting device 99 and move the switch 79 to its -iirst position in which the lead 80 is connected only to the lead 78. However, when the Valve 72 is moved to full open position, the switch 100 operates to cause the transmitting device 99 to move the switch 79 to its second position by which lead 80 is connected only to the lead 98. Also, the switch 101 is designed to operate when the valve 94 is moved to closed position to etect energization of the transmitting device 99 for moving the switch 79 to its iirst position and establish a connection between leads 80 and 78. The switch 100 also operates responsively to the ow meter 67 through lead 6 104 and to a pressure measuring device 105 connected to the conduit 66 through a conduit 106. Should the rate of ow of the low pressure stream drop below required limits, the switch 100 operates to effect movement of the switch '79 to its second position and connect leads S0 and 98 irrespective of the position of valve 72.

In operation, the blower control 43 is set to establish the desired rate of flow of blast gas through the compressor 30, the ratio control 56 is adjusted to establish a desired percentage of oxygen enrichment and the moisture control 81 is set to establish the desired quantity of moisture in the blast gas blown to the furnace. When the desired moisture content of the blast gas is less than the maximum moisture that may be added to the blast gas through the introduction of low pressure'steam, as determined by the dew cell 73 and the control valve 69, the moisture control 81 is connected through lead 80, switch 79 and lead 78 to the' transmitting device 77 to maintain the moisture content of blast -gas substantially equal to the desired value by controlling the valve 72. However, when the desired moisture content is greater than the maximum moisture that may be provided by the flow pressure steam source, the valve 72 will move to its full open position at which time switch 100 operates to energize the transmitting device 99 and move switch 79 to its second position and thereby place the high pressure steam control valve 94 under control of the moisture control 81. The quantity of high pressure steam entering the blast gas on the discharge side of the compressor through conduit 95 is substantially equal to the difference between the moisture indicated by the dew cell 73, that is, the natural moisture plus the moisture provided by the low p-ressure steam source, and the desired moisture content. The quantity of high pressure steam entering the blast gas is indicated by the meter 92 and the rate of flow of blast gas to the lfurnace may be easily calculated. Variations in the natural moisture content of the air are automatically compensated for by controlling the iiow of low pressure or high pressure steam entering the system through operation of valves 72 or 94.

With this `arrangement it is possible to introduce into the blast gas any desired quantity of moisture, which may be maintained substantially constant irrespective of variations in the natural moisture content of the air, while at all times utilizing the maximum possible quantity of 4available low pressure steam. Since in most blast furnace installations an ample quantity of low pressure steam is obtainable without expense, while providing high pressure steam adds to the cost of the product, this yfeature of the invention results in substantial savings in View of the large quantities of moisture blown into the furnace during each twenty-four hours of operation.

ln the embodiment of the invention shown in Figure 2 of the drawings the oxygen stream and the stream of low pressure steam are introduced -into the blast gas in the conduit 38 on the suction side of the compressor and the high pressure steam is introduced through conduit into conduit 34 on the discharge side of the compressor while the venturi measuring device 42 is positioned in the conduit 34 on the discharge side of the compressor downstream of the high pressure steam conduit 95 yand upstream of the conduit 84 leading to the dew cell 82. This arrangement operates in a manner similar to the arrangement shown in Figure l with the exception that the total blast gas blown to the furnace tio-ws through the venturi measuring device 42 Land the quantity of blast gas entering the furnace may be established by the blower control 43. This arrangement eliminates the necessity of utilizing a high pressure steam iiow meter, such as the iiow meter 92 of Figure l in order to ascertain the total blast entering the furnace. Of course, a flow meter such Ias the meter 92 may be included in the conduit 95 to indicate the quantity of high pressure steam entering the blast gas.

In the embodiment of the invention shown in Figure 3 of the drawings, steam from the -low pressure source 6.5

'Y isconductedVj byl conduit-1^10to the low pressure4 steam -controlfvalve 72 and then fed l to conduit 111' having Ya discharge'end 112 terminatingy within the conduit 38'on Y is passed by 'way of conduit114, control valve 115, and

conduit 116 to the conduit 34 on the'discharge side ofthe compressor upstream'of the dew cellV conduit 84. n The means `for controlling the compressor 30 'and-for establishing thepercentage ofoxygen enrichment are similar to the arrangements shown in Figure 1. In Figure 3 there is also illustrated one` of a plurality of stoves 120 having an inlet conduit 121 connected to the conduit 34 and an outlet conduit 122 connected to the conduitV 35 with a` by-pass 123 having a control valve f124 connected betweenv the conduits 121 and 122.

In operation ofthe arrangement shown in Figure 3,

' the'moisture control 81 functions to position the low pressure steam control valve 72 and thereby control the quantity of low'pressure steam introduced into the blast gas upstream of the compressor and maintain a substantially constant quantity of moisture in the blast gas. blown to the furnace, as determined by the moisture control 81, irrespective of variations of natural moisture contentof atmospheric air entering the conduit 38. When high quantities of moisture in excess of the total moisture that may be obtained by adding low pressure steam to the suction side of the compressorV are required in the blast gas, valve 11S is manually adjusted so that -a fixed quanf tity of steam from the hi-gh pressure source is fed through conduit 116 -into the blast gas on the discharge side of the compressor. For example, it is assumed that 20 grains of moisture per cubic foot of blast gas is required, that the natural moisture content of the atmospheric air is 6 grains per cubic foottand that the temperature conditions of the atmospheric air are such that a maximum of grains per cubic foot of blast Igas may be maintained on the suction side of the compressor through the addition of low pressure steam, the high-pressure steam control valve 1115 would be manually adjusted to feed l()V grains of moisture per cubic foot of blast gas into the conduit 34, the quantity Vof moisture being` indicated Von the meter 92. The moisture control 81, being set to mainpresser and. highfpressure. steam Von the discharge Vside of the compressorin anovel manner that insures utilization VYof the maximum quantity of loW pressuresteamjn establishing the desired moisture content. Y Y

I Although several embodiments of the Vinvention have beenvdisclosedianddescribed herein, Aitis to be expressly understood that various Vchanges and substitutions may be made Vtherein Without departing from the 'spirit ofthe invention as well understood by those skilled in the `art. For example, in the arrangement shown in Figure 3 of the l drawings, theventuri measuring device 42 may be located in the conduit 34 on the discharge side ofthe compressor 30 in the manner shown in Figure 2 of the drawings, if desired. Reference therefore will be hadV to the appended claims forV a definition of the limits of the invention.

What-is claimed is: A

l; In a blast furnace installation including a blast furnace `having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas to the tuyere means, ymeasuring means Vfor measuring the rrate ofv howY of blast gas through-the compressor means, Vcontrol means operative responsively to the measuring means for controlling the compressor means, means including rstconduit means for introducing low pressure Water vapor into blast gas on the suction side ofthe compressor'me'ans, means including second conduit means for introducing relatively high pressure water vapor into blast gas on theadischarge side of the compressor means, moisture measuring means for measuring the moisture content of blast Ygas blown to the tuyere means, and moisture control means operative responsively to the moisture measuring means for controlling Y the flow of Water vapor in the iirst conduit means.

tain a moisture Vcontent of 20 grains per cubic foot of blast Y gas then functions to control the valve 72 through the transmitting device 77 and supply a quantity of low pressure steam equal to 5 grains of moisture perrcubicfoot of bl-ast gas. Any variations in the natural moisture content of the air would cause an lincrease or decrease in theV ow of low pressure steam to maintain the total moisture entering the furnace at the desired' quantity of 20 grains per cubic ifoot of blast gas. Means `may be provided Vfor operating the high Vpressure steam control valve 115 responsively to the blower control 43 so that the ow of high pressure steam to the blast gas is materially decreased orY shut off at times Vwhen the Wind blown to the furnace is severely reduced such `as during tapping operations, yfor example. Y

'There is thus lprovidedby the present invention novel Y apparatus for controlling the composition of blast jglas such as for establishing and maintaining the percent of oxygen enrichment and the quantity of'moisture in blast gas substantially in accordance Withfpredetermined ref quirements.V The arrangement is suc-h that a wide range of moisture content may be maintained in blast gas'blown Y to the furnace, suchras from about 3 grains to 80- or more grains per cubic foot of blastgas, by the introducjtionoflow-pressurelsteam on the suctionside -of the y'com- 2. In a blast furnace installation including aY blast furnace having tuyere Vmeans through which lblast gas is discharged into the'furnace, means including compressor means for blowing blast-gas to the-tuyere means, the blast gas including atmospheric air, measuring meansffor measuring the rate of ilowof Vblast gas throughthe compressor means, control means operative'responsively'to'the measuring means for controlling the compressor means, means including first conduit means for introducing low pressure water VaporV into blast gas on the suction.` side of the compressor means, means including Vsecond conduit means for introducing relatively 4hi-ghpressure water vapor into blast gason the discharge side of Ythe compressor means, moisture lmeasuring means for measuring the V'moisture content of blast -gas blown vto the tuyere means, Vmoisture control'meansconnected to .the moisture measuring means and lincluding comparing means for comparing the moisture content of blast gas blown tothe tuyere means and a predetermined moisture content, and means for'controlling the rate of ow of water vapor in the first conduit means responsively to the comparing means to maintain a moisture content in the blast gas substantially Vcorresponding to the predetermined moisture, content irrespective of lvariations of the natural moisture content of the atmosphericair. Y

3. YIn a blast furnace installation including a blast furnace having tuyere means through which blast ygas is discharged into. the furnace, meansincluding compressor means for'blowing blast gas to the tuyere means-,measuring means .for measuring the rate of ow of Vblast gas `throughthe compressor means, control means operative responsivelyv to themeasuring means` for` controlling the compressor means, means including first conduit means for introducing low pressure water vapor into blast gas on the suction side ofthe compressor means, means including second conduit means for introducing a` substantially constant quantity of relatively high pressure water vapor into blast gas onthe discharge side ofthe cornpressor means, moisture* measuring means for measuring the moisture contentof blast gas blown-to the` tuyere Y-mean'srand moisture control means.operativerespnnsively 9 to the moisture measuring means for controlling the ow of water vapor in the first conduit means.

4. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas to the tuyere means, the blast gas including atmospheric air, measuring means for measuring the rate of ilow of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means including first conduit means for introducing low-pressure water Vapor into blast gas on the suction side of the compressor means, means including second conduit means for introducing a susbtantially constant quantity of relatively high pressure water vapor into blast gas on the discharge side of the compressor means, moisture measuring means for measuring the moisture content of blast gas blown to the tuyere means, moisture control means connected to the moisture measuring means and including comparing means for comparing the moisture content of blast gas blown to the tuyere means and a predetermined moisture content, and means for controlling the rate of tlow of water Vapor in the first conduit means responsively to the comparing means to maintain a moisture content in the blast gas substantially corresponding to the predetermined moisture content irrespective of variations of the natural moisture content of the atmospheric air.

5. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas to the tuyere means, measuring means for measuring the rate of llow of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means including irst conduit means for introducing low pressure water vapor into blast gas on the suction side of the compressor means, means including second conduit means for introducing relatively high pressure water vapor into blast gas on the discharge side of the compressor means, moisture measuring means for measuring the moisture content of blast gas blown to the tuyere means, and means responsive to the measuring means for controlling flow of water vapor through the rst conduit means and through the second conduit means.

6. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas tov the tuyere means, the blast gas including atmospheric air, measuring means for measuring the rate of flow of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means including first conduit means for introducing low-pressure water vapor into blast gas on the suction side of the compressor means, means including second conduit means for introducing relatively high pressure water Vapor into blast gas on the discharge side of the compressor means, moisture measuring means for measuring the moisture content of blast gas blown to the tuyere means, moisture control means connected to the moisture measuring means and including comparing means for comparing the moisture content of blast gas blown to the tuyere means and a predetermined moisture content, and means for controlling the flow of water vapor in the rst conduit means and in the second conduit means responsively to the comparing means to maintain a moisture content in the blast gas substantially corresponding to the predetermined moisture content irrespective of variations of the natural moisture content of the atmospheric air.

7. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas into the tuyere means, measuring means for measuring the rate of oW of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means for introducing atmospheric air to the suction side of the compressor means, means including rst conduit means for introducing water vapor into blast gas on the suction side of the compressor means, means for controlling the ilow of water vapor in the rst conduit means to limit the total moisture of blast gas on the suction side of the compressor means below a critical level that would result in condensation of water vapor, means including second conduit means for introducing water vapor into blast gas on the discharge side of the compressor means, and means for controlling the llow of water Vapor through the first conduit means and the second conduit means responsively to the moisture content of blast gas blown to the tuyere means, the last-named means including means for controlling the flow of Water vapor through the rst conduit means responsively to variations of moisture content of blast gas blown to the tuyere means less than said level, and means for controlling the low of water vapor through the second conduit means responsively to variations of moisture content of blast gas blown to the tuyere means greater than said level.

8. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas to the tuyere means, measuring means for measuring the rate of ilow of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means for adding oxygen rich gas to the blast gas, means for measuring the ow of oxygen rich gas, means for comparing the ilow of oxygen rich gas and the rate of flow of blast gas through the compressor means to determine the percentage of oxygen in blast gas blown to the tuyere means, means including first conduit means for introducing low pressure water Vapor into blast gas on the suction side of the compressor means, means including second conduit meansl for introducing relatively high pressure water vapor into blast gas on the discharge side of the compressor means, moisture measuring means for measuring the moisture content of blast gas blown to the tuyere means, and moisture control means operative responsively to the moisture measuring means for controlling the flow of water vapor in the first conduit means.

9. In a blast furnace installation including a blast furnace having tuyere means through which blast gas is discharged into the furnace, means including compressor means for blowing blast gas to the tuyere means, the blast gas including atmospheric air, measuring means for measuring the rate of iiow of blast gas through the compressor means, control means operative responsively to the measuring means for controlling the compressor means, means for adding oxygen rich gas to the blast gas, means for measuring the ilow of oxygen rich gas, means for comparing the ow of oxygen rich gas and the rate of flow of blast gas through the compressor means to determine the percentage of oxygen in blast gas blown to the tuyere means, means including rst conduit means for introducing low pressure water vapor into blast gas on the suction side of the compressor means, means including second conduit means for introducing relatively high pressure water vapor into blast gas on the discharge side fthe compressor means, moisture measuring means for measuring the moisture content of blast gas blown to the tuyere means, moisture control means including comparing means for comparing the moisture content of blast gas blown to the tuyere means and a predetermined moisture content, and means for controlling the rate of flow of water vapor in the first conduit means responsively to the comparing means to maintain a moisture content in the blast gas `substantially corresponding to the Vprede-l v Y means for blowing blast gas to the ituyere means, meas-V uring means for measuring the rateof ow of blast gas through the compressor means, controlmeansoperative responsively to the measuring means forcontrolling the compressor means, means for adding voxygen rich gas to the blast gas, means for measuring the ow of orygen riclrgas, means'forcomparing theflowvroxygen rich gasV and the ratel of ow ofblast/gas-throughthe compressor means to determinathe/percentage of oxygen' in blast gas Iblown to theirkry/ere means, means including first conduit means forY introducing low pressure Water vapor into blast gas on the suction side.' of the compressory means, means including. second conduit means forY introducing a substantially constant quantity of relatively/highY pressure Water vapor into blastV gas on thel discharge( side of the compressor means, moisturerneasuring means kfor measuringthe moisture Acontent of blast gasblown to the Y means and the second control means.

including meansy operable responsivelyLto .the irstz ,controlV 13.Y In ablast' furnace installationv as de Vedfirrclairn l1, means independent of thefrstcontrolmeansoperable to maintain the moisturey contentofblast gasonthezsuc- Y tion side of the compressor means belowV a VcriticalV value thatA would result: in condensationofgwater vapor, and meansloperative responsively tothe lastfnamed means for effecting control'of the secondV control meansV responsively to the measuring means. ,v iv i 14.1111 a blast furnaceV installation. including' ablast furnace having tuyere means through which blast Vgas is discharged into the furnace, means'including compressor tuyere means, and moisture control means operative re-V sponsively to the moisture measuring means for controlling the flow of Water vapor in the, rst conduitimeans'. V

11. VIn a blast furnace. installation including` ablast furnace having tuyere means'througlrV whichvblast gas is discharged into the furnace, meansincludingcompressor means for blowing blast gas to the tuyereV means,r measuring means for measuring the rate of ow Vof blast gas through the compressor means, control means operative Vresponsively to the measuring means for controlling the compressor means,imeans= including rst conduit means .Y for introducing low pressure water vapor into blast gas on the suction side of the compressor means, means includi ingv second conduit means for introducing relatively high pressure `waterlvapor, into blast gas on the discharge side of the-.compressor means, moisture measuring rneansifor measuring the Vmoisture' content of blast -gas blown toV the tuyere means, rst control means for controlling'the ow of'low pressure water vapor through the 'first .con-

duit means, second control means for controlling the iiow of relatively high pressure water vapor through-the Vsecond conduit means, and means for connecting the moisture measuring means to the rst'control means when the moisture content of blast gas blown to the tuyere means' is belowa` predetermined level and for connecting the moisture measuring means to the second control means when the moisture'content of blast gas blown to the tuyere means is above the predetermined level. y

12. In a blast furnace installation as defined in claim l1, with the means for connecting the moisture measuring means to the -frst control means and for connecting means forblowing blastgasto the'tuyere means, measuring'means for measuring'the ratejof 'flowaofblastgas through the compressor means,.controlmeans `operative res'ponsivelyV to the measuring meansforcontrolling the compressorY means, means,l for. introducing .atmospheric air to the suction sidezofihe compressor means', means including rst conduit meansfor'introducing'low pressure. water vaporY into blast' gas onithe suction side of thezcompressor means,'means including secondconduit means for introducing relatively highpressure water vapor into blastV gas on thedischarge side ofthe compressor means, moisturemeasuring means Vfor;r`neasuring the `moisture `content of blast gas blown to'theltuyeremeansatirst: con-l itrol meansfor controlling the ow oflow pres'sureriwater vapor through the. first conduit means;V secondV control means for controlling the owiiofhi'ghfpressure: water vaporV through the second conduit means, switch. means connected to the moisture measuring means and operable in one position to connectthe; moisture measuring/means tothe rst ycontrol means andV operable in-a` secordzposi-l tionfto connect the' moisture' measuring means to: the second control means, meansfor. operating the'- switch means to .the iirst and second positions,v means .operative responsively to a predetermined position in the'ist coni 14, means yfor measuring the moisture content of blast gas on the .suction side-of the compresormeans and for controlling the ow of low pressuresteamfto `the first conduit means independently of the first control means, means operable responsivelyvto the rate offiow of the lowpressure steaminV the-first conduit means-'for moving the switch means to the second position.

V'References Cited inthe Ytile of this patent `1 UNIIEDy STATES PATENTS VCarr-ier Y 'Oet. 9, 1945 2,448,199 Vollrath V Aug. 31,1948 2,778,018 Strassbu'rger K Ja'n. 15,'1957 

